Electromagnetism part 2

Units

Electromagnetic units are part of a system of electrical units based primarily upon the magnetic properties of electric currents, the fundamental SI unit being the ampere. The units are:

• ampere (current)
• coulomb (charge)
• farad (capacitance)
• henry (inductance)
• ohm (resistance)
• volt (electric potential)
• watt (power)
• tesla (magnetic field)
• weber (flux)

In the electromagnetic cgs system, electrical current is a fundamental quantity defined via Ampère's law and takes the permeability as a dimensionless quantity (relative permeability) whose value in a vacuum is unity. As a consequence, the square of the speed of light appears explicitly in some of the equations interrelating quantities in this system.

SI electromagnetism units v • d • e
Symbol[2]	Name of Quantity	Derived Units	Unit	Base Units
I	Electric current	ampere (SI base unit)	A	A (= W/V = C/s)
Q	Electric charge	coulomb	C	A·s
U, ΔV, Δφ; E	Potential difference; Electromotive force	volt	V	J/C = kg·m2·s−3·A−1
R; Z; X	Electric resistance; Impedance; Reactance	ohm	Ω	V/A = kg·m2·s−3·A−2
ρ	Resistivity	ohm metre	Ω·m	kg·m3·s−3·A−2
P	Electric power	watt	W	V·A = kg·m2·s−3
C	Capacitance	farad	F	C/V = kg−1·m−2·A2·s4
E	Electric field strength	volt per metre	V/m	N/C = kg·m·A−1·s−3
D	Electric displacement field	Coulomb per square metre	C/m2	A·s·m−2
ε	Permittivity	farad per metre	F/m	kg−1·m−3·A2·s4
χe	Electric susceptibility	(dimensionless)	-	-
G; Y; B	Conductance; Admittance; Susceptance	siemens	S	Ω−1 = kg−1·m−2·s3·A2
κ, γ, σ	Conductivity	siemens per metre	S/m	kg−1·m−3·s3·A2
B	Magnetic flux density, Magnetic induction	tesla	T	Wb/m2 = kg·s−2·A−1 = N·A−1·m−1
Φ	Magnetic flux	weber	Wb	V·s = kg·m2·s−2·A−1
H	Magnetic field strength	ampere per metre	A/m	A·m−1
L, M	Inductance	henry	H	Wb/A = V·s/A = kg·m2·s−2·A−2
μ	Permeability	henry per metre	H/m	kg·m·s−2·A−2
χ	Magnetic susceptibility	(dimensionless)	-	-

Electromagnetic phenomena

With the exception of gravitation, electromagnetic phenomena as described by quantum electrodynamics (which includes as a limiting case classical electrodynamics) account for almost all physical phenomena observable to the unaided human senses, including light and otherelectromagnetic radiation, all of chemistry, most of mechanics (excepting gravitation), and of course magnetism and electricity. Magnetic monopoles (and "Gilbert" dipoles) are not strictly electromagnetic phenomena, since in standard electromagnetism, magnetic fields are generated not by true "magnetic charge" but by currents. There are, however, condensed matter analogs of magnetic monopoles in exotic materials(spin ice) created in the laboratory.